FocusShifter - Follow Focus and Rack Focus for DSLR and Mirrorless Camera Lens Nail your focus: The re-useable focus marker board allows you to create marks for your focus points using a dry-erase marker Hard stops: Using simple clips that attach to the focus marker board Simple to install: To attach the shifter, simply slip it over the lens Easy and smooth: The shifter allows you to smoothly Pull focus without any jarring starts or stops For photographers too: Using the shifter improves manual focus speed and accuracy when taking photographs